Leading article: An inevitable response

The news that the United States has boosted the missile defences of a number of Gulf states, including the United Arab Emirates, Qatar, Bahrain and Kuwait, offers fresh, if depressing, confirmation of the failure of Barack Obama's initiative to put relations with Iran on a new footing. It is no secret that these early warning radar systems are intended primarily to counter Iranian attacks in the event of a possible military conflict with Tehran. It is back to business as usual, in other words, with the threat of war-war replacing a brief, fruitfless try at jaw-jaw.

It was only a year ago that the new US president hoped to make Iran an example of a new foreign policy based on dialogue rather than the "big stick" approach favoured by George Bush. How long ago that seems. The onus for the failure of Mr Obama's attempt at doveish diplomacy lies with the Ahmadinejad regime. It calculated it had more to lose than gain at home if it allowed the tension with the Great Satan to relax, and so rebuffed him. America's reversion to a policy of military containment backed up by tightened sanctions was therefore inevitable and has been fleshed out recently by President Obama in his State of the Union address, by Hillary Clinton, the Secretary of State, and by General Petraeus, head of US Central Command.

None of this means Washington now considers military action against Iran inevitable, likely or desirable. On the contrary, the White House hopes arms sales to the Gulf states will convince Israel that a pre-emptive military strike aimed at disabling Iran's nuclear ambitions is unnecessary.

There is a logic to this argument. Yet it is hard to feel much confidence in the benign outcome of what amounts to an arms race. Nor is it certain that Iran will draw the intended conclusions from this build-up. The most worrying thing about Iran is that it is weak and strong at the same time. It is a regional superpower, thanks to the eclipse of Iraq, yet the government is also becoming afraid of its own population and is increasingly paranoid and unpredictable in consequence. Whether the new military muscle of the pro-Western Gulf states that Tehran despises will act as a restraining factor on Iran remains to be seen.